Water collection areas, pumping stations and pipelines

The Waiwhetu artesian aquifer is a zone of water-holding sand, gravel and boulders beneath the Hutt Valley. It provides around 40 percent of the annual water supply.

Find out more about the aquifer

There are two major water collection areas in the Hutt Valley.

Hutt River supply

Rainwater collects in tributary streams that flow into the Hutt River. We have a weir (low dam) at Kaitoke, just north of Upper Hutt, where water is taken from the river, strained to remove sticks, leaves and silt, and piped through tunnels to the Te Marua water treatment plant. We are allowed to take up to 150 million litres of water per day from the Hutt River, provided an adequate flow is maintained downstream of the weir.  The Hutt Water Collection area provides about 40 percent of the water we supply each year.

Macaskill Lakes

We have two large storage lakes at Te Marua as back-up to the Hutt River supply. The lakes are filled from the river when it is clean and there is plenty of water available. Stored water is pumped back to the treatment plant when there is not enough water in the river to meet public demand, when the river is too dirty - after heavy rainfall - or when it is in flood and the intake is closed to prevent rocks and gravel from entering the intake pipes. The Macaskill Lakes are 16 metres deep and have a combined useable capacity of approximately 3,000 million litres, or enough to meet average water use for 20 days.

The Wainuiomata/Orongorongo Water Collection Area is part of the Remutaka Ranges to the east of Wainuiomata. The collection area covers 7,600 hectares.

Five low dams (weirs) with intake pipes provide water to the Wainuiomata Treatment Plant. Weirs on the Wainuiomata River and George Creek provide around 15 percent of our annual water supply. In the Orongorongo Valley, weirs on the Orongorongo River, Big Huia Creek and Little Huia Creek provide around five percent of annual water supply. A 3.2 kilometre long access and pipeline tunnel links the Orongorongo Valley intakes to the Wainuiomata Valley.

We must leave a minimum water flow equivalent to 8.6 million litres per day in the Wainuiomata and Orongorongo Rivers, downstream of our weirs. Unlike Te Marua, there is no untreated water storage at Wainuiomata. If river levels are very low or the rivers are in flood the treatment plant is turned off temporarily.